Green bike lanes fade to black

Miles of bright green shared-lane markings were painted on city streets last fall, intended to raise the visibility of Minneapolis’ growing network of on-street bicycle lanes. But those markings are a lot less visible just six months later.

The surprisingly short lifespan of the green paint was noticed by some cyclists this spring, including Simon Blenski, a planner in the city’s Bicycle and Pedestrian Program.

“I’ve kind of determined the effective life span of the paint we’re using is three to six months, about, and we want that to last much longer,” Blenski said. “It’s not doing that.

“It really wasn’t a harsh winter, yet a lot of the markings didn’t last that well,” he added, noting that snowplows are typically street markings’ worst enemies.

The markings’ longevity may improve over time, as layers of paint build up in the pockmarked pavement, or as city engineers learn to position them out of the path of car tires. But some high-traffic areas may require a more durable, and probably more expensive, solution, said Steve Mosing, a city traffic operations engineer.

“This is really new, so not a lot of cities are doing this,” Mosing said. “And I can tell you Chicago probably has a few [shared-lane markings], but as far as a real snow city, Minneapolis is probably one of the first to do this in the country. We’re going to continue to look at and monitor where these go.”

A green latex paint similar to ordinary house paint is used both for shared-lane markings — like those on Bryant Avenue south of Lake Street — and also to mark “conflict zones,” or places where cars must cross over bicycle lanes to turn. On Bryant Avenue this spring, the shared-lane markings painted just last fall already had faded to a dull grey-green, a hue not too different from the underlying asphalt.

Even worse was an Oak Grove Street crosswalk near the Walker Art Center that is part of an off-street bicycle path linking Southwest neighborhoods to Downtown. By March, the bright green paint that once filled the crosswalk was almost entirely worn away.

Faring much better than the latex paint is a thermoplastic lane marking applied last year to parts of a 15th Avenue Southeast near the University of Minnesota campus. The bright green, reflective plastic is melted into the street surface with heat, and is so far earning high marks from public works crews, Blenski said.

“Internally, public works is really happy with how 15th Avenue is holding up,” he said.

The thermoplastic is durable, but expensive. The city paid a contractor $16,400 to apply about 840 square feet of the material to 15th Avenue Southeast in 2011.

By comparison, the city spent about $69,000 last year to have a contractor apply 28,900 square feet of the green paint to city streets at cost of $2.39 per square foot. Those figures don’t include green bicycle lanes striped down either side of Hennepin Avenue through Downtown, since city crews first painted those lanes in 2010.

Thermoplastic is one, but not the only, option for high-traffic areas like the Oak Grove Street crosswalk. The city also uses a spray-on epoxy product or plastic tape known as “poly preform” to place bicycle symbols on streets in various locations, sometimes in conjunction with painted shared-lane markings.

Jon Wertjes, the city’s director of traffic and parking services, said almost every stripe and lane marking on city streets gets repainted on an annual basis. Public works crews stripe streets at night, typically starting shortly after spring street sweeping, Wertjes said.

Painted bicycle markings make up just a fraction of the markings on city streets, but it’s a growing share of the total. In 2011, a federal grant funded a major expansion of the city’s on-street bicycle lane network, which grew by more than 40 percent to nearly 80 miles. More projects are planned for this summer.

Mosing estimated 10–15 percent of the paint on city streets was used to mark bicycle lanes. Based on last year’s street street-striping budget, the city would spend about $16,500–$25,000 per year to repaint the existing bicycle markings, he said.

Mosing added that 2011 spending on bicycle lane painting wasn’t a good benchmark for future costs, since that work was mainly done by a contractor. The city recently purchased its first new street striper in 15 years, meaning city crews will handle the work this summer and in years ahead.